Visible image displays (capable of displaying visible images to the human eyes), such as the full-color displays, are well known and are based on a variety of technologies such as cathode ray tubes, liquid crystal, and solid-state light-emitting devices including inorganic Light-Emitting Diodes (LEDs) and Organic Light-Emitting Diodes (OLEDs). In a common full-color display (or RGB display), each pixel is composed of three primary color radiation subpixels (or color elements), i.e., red, green, and blue color radiation subpixels. By combining the emission, transmission, or reflection from each of these three primary color radiation subpixels in an additive color system, a wide variety of colors can be achieved and images can be displayed with a proper drive circuitry. There are numerous types of full-color displays disclosed in the prior art. The non-limiting examples can be found in U.S. Pat. Nos. 6,882,383, 6,864,875, 6,855,438, 6,838,819, 6,791,258, 6,787,995, 6,384,529, 6,142,637, 6,066,357, 5,965,907, 5,937,272, 5,712,651, 5,583,349, 5,003,179, 4,801,844, 4,799,050, and 4,689,522.
There is another type of display, called invisible image display (capable of displaying invisible images to the human eyes, but the images could be perceived by the human eyes only with a wavelength conversion device), such as an infrared display (or IR display). The invisible image display can also be made based on the technologies such as liquid crystal and solid-state light-emitting devices. In an IR display, each display pixel can be composed of an infrared device. Each infrared device in the IR display can emit, transmit, or reflect infrared wavelength. Infrared images can be displayed on the IR display with a proper drive circuitry. And the infrared images can be perceived by the human eyes through night vision goggles or other wavelength conversion devices. IR displays have been disclosed, such as, in U.S. Pat. Nos. 4,930,236 and 4,724,356; and in JP 02,094,340.
It is well known that the visible image displays are widely used in our daily life. The invisible image display, such as the IR display, can also have its special applications. For example, it can be used as a personal night vision display in a combat field or a navigator display in an aircraft or in a spacecraft.
In some cases, for example, as personal equipment for a soldier in a future combat field, both a visible image display and an invisible image display are needed. The visible image display is used for the daylight vision and the invisible image display is used for the night vision with a wavelength conversion device. In this situation, any personal equipment with lightweight, low power consumption, and easy-to-use is critical to the soldiers. However, equipped with two displays would increase the carrying weight, demand more electrical power consumption, need longer time to switch to another display, and even increase the risk to life in the combat field.
Cok et al. disclosed an OLED display having more than 3 subpixels in each pixel in U.S. Pat. No. 6,570,584 B1, wherein the 4th subpixel is an OLED which can have an emission outside the gamut defined by red, green, and blue. The 4th subpixel can be an infrared OLED. According to the disclosure, the 4th subpixel is to expand the gamut or encode with additional information, and the subpixels in each pixel are made of OLEDs.